Thermoplastic resin composition with improved uv resistance

ABSTRACT

Thermoplastic resin composition comprising: (a1) at least one styrene-acrylonitrile copolymer component A1, (a2) at least one acrylonitrile styrene acrylate graft copolymer A2 as impact modifier, (a3) optionally at least one thermoplastic polymer A3 other than components A1 and A2, (b) at least one pigment B, (c) at least one hindered amine UV light stabilizer C, and (d) optionally further polymer additives D, other than components B and C, wherein the UV stabilizing component(s) present in the thermoplastic resin are only hindered amine UV light stabilizer(s) C.

The invention relates to a thermoplastic styrene copolymer resin composition with improved UV resistance comprising at least one styrene-acrylonitrile copolymer, at least one acrylonitrile styrene acrylate graft copolymer, at least one pigment and at least one hindered amine UV light stabilizer. The invention further relates to a method for the preparation of said thermoplastic resin composition, the use of said thermoplastic resin composition, and molded articles prepared from said thermoplastic resin composition.

Acrylonitrile-styrene-acrylates (ASA) are thermoplastic resin materials with intrinsic UV resistance due to the lack of reactive carbon-carbon double bonds. However, in order to use such thermoplastic resin compositions in outdoor applications under sometimes harsh conditions such as rain and intensive UV exposure by sunlight, UV stabilizers are necessary. Missing UV stabilization leads to inferior mechanical properties such as reduced impact toughness, reduced stress-strain characteristics, reduced resistance to chemicals, discolorations such as yellowing of the thermoplastic resin composition, loss of transparency of transparent thermoplastic resin compositions, surface damage resulting in parts of the surface being washed off giving rise to irregular scattering of reflected light, which is perceived as lightening or graying of the thermoplastic resin composition.

In addition, thermoplastic resin compositions often comprise at least one pigment. The pigments themselves already have a significant influence on the UV stability of the thermoplastic resin composition. Especially in the case of iron containing pigments, lower UV resistance can be observed. This results for example in a larger color shift dE of the thermoplastic resin compositions comprising iron pigments observed after artificial weathering compared to thermoplastic resin compositions comprising pigments not based on iron.

UV absorbers from the class of hydroxyphenyl-benzotriazoles are well known as UV stabilizers for polymers in general. Another class of UV stabilizers is the group of hindered amine lights stabilizers (HALS) used for stabilization of all sorts of polymers. UV stabilizers are commonly used as mixtures of several classes of UV stabilizers for best UV stabilization. UV stabilizer mixtures are often selected for the synergistic effects obtained by combination of UV stabilizers of different classes.

A general overview on the different aspects of ASA thermoplastic resins is provided in N. Niessner, Practical Guide to Structures, Properties and Applications of Styrenic Polymers; United Kingdom: Smithers Rapra Technology Ltd, 2013, Chapter 4. Thermoplastic resin compositions with improved resistance to weathering are well known in the art.

US 2016/060446 (Samsung) discloses thermoplastic resin compositions which can realize good coloring properties and weathering resistance while providing a high quality appearance. This is achieved by applying both a UV stabilizer and a UV absorber.

U.S. Pat. No. 4,877,826 discloses weatherable styrenic polymer blends comprising polyalkylene glycol. However, the polymer blends show low initial gloss and only limited weatherability. U.S. Pat. No. 4,692,486 discloses a synergistic mixture of low-molecular and high-molecular polyalkylpiperidines, i.e. mixtures of different HALS as UV stabilizers in polypropylene, polyurethane and polystyrene. DE-A 10316198 teaches ternary stabilizer mixtures of different UV stabilizers for use in various thermoplastic resin compositions. EP-A 2593507 discloses weathering-resistant styrene copolymer moulding compositions. Different high gloss ASA resin compositions are described each comprising two different HALS and additionally styrene acrylonitrile oligomer. WO 2012/007268 relates to stabilized acrylonitrile-styrene-acrylic ester molding compositions comprising different UV stabilizers.

There is however a continuous need for thermoplastic resin compositions with improved UV resistance. It was one objective of the present invention to provide thermoplastic resin compositions which comply with the above identified technical needs. This was achieved by the present invention as described herein below and as reflected in the claims.

The term “copolymer” as used herein describes a polymer which is formed by polymerizing two or more different monomers. The polymer may be composed of only one linear chain or may be branched. The monomer units in the copolymer may be alternating regularly forming an alternating copolymer, may repeat periodically forming a periodic copolymer, may be statistically distributed forming a statistical copolymer, or may form different blocks, forming a block copolymer.

The present invention is described in the following by disclosing various aspects of the invention. Combinations of different aspects pertaining to different features are also envisaged. All ratios presented in wt.-% are based on the total weight of the thermoplastic resin composition unless otherwise indicated.

The invention relates to a thermoplastic resin composition comprising (or consisting of):

-   (a1) at least one styrene-acrylonitrile copolymer component A1, -   (a2) at least one acrylonitrile styrene acrylate graft copolymer A2     as impact modifier, -   (a3) optionally at least one thermoplastic polymer A3, other than A1     and A2, -   (b) at least one pigment B, -   (c) at least one hindered amine UV light stabilizer C, and -   (d) optionally further polymer additives D, other than components B     and C,     wherein the UV stabilizing component(s) present in the thermoplastic     resin are only hindered amine UV light stabilizer(s) C.

In one aspect of the present invention, the thermoplastic resin composition comprises (or consist of) from 70.0 to 99.4 wt.-% of components A1, A2, and optionally A3, and from 0.5 to 7.0 wt.-% of component B, and from 0.1 to 1.5 wt.-% of component C.

In another aspect of the present invention, the thermoplastic resin composition comprises of from 89.0 to 99.3 wt.-% of A1, A2, and optionally A3, and from 0.5 to 7.0 wt. % of component B, and from 0.1 to 1.5 wt.-% of at least one hindered amine UV light stabilizer C, and from 0.1 to 2.5 wt.-% of at least one further polymer additive D. In a further aspect, component B is present in the range of from 0.7 to 5.0 wt.-%. In another aspect, component B is present in the range of from 0.8 to 4.0 wt.-%. In another aspect, component B is present in the range of from 1.0 to 2.0 wt.-%.

In a further aspect, component C is present in the range of from 0.2 to 1.25 wt.-%. In another aspect, component C is present in the range of from 0.3 to 1.0 wt.-%. In another aspect, component C is present in the range of from 0.4 to 0.8 wt.-%. In another aspect Component D is present in the range of from 0.2 to 2.0 wt.-%. In a further aspect, component D is present in the range of from 0.3 to 1.75 wt.-%. In another aspect, component B is present in the range of from 0.7 to 5.0 wt.-% and component C is present in the range of from 0.2 to 1.25 wt.-%.

The styrene-acrylonitrile copolymer A1 and the acrylonitrile styrene acrylate graft copolymer A2 form together the acrylonitrile styrene acrylate terpolymer (ASA). This terpolymer is either used on its own or as blend with for example polyamide (ASA/PA) or with polycarbonate (ASA/PC). The spherical particles of crosslinked acrylate rubber (A2.1) are chemically grafted with styrene acrylonitrile copolymer chains (A2.2), and are embedded as acrylonitrile styrene acrylate graft copolymer (A2) in a styrene acrylonitrile matrix (A1).

The ratio of styrene-acrylonitrile copolymer A1 to acrylonitrile styrene acrylate graft copolymer A2 is in the range of from 10 wt.-% to 95 wt.-% based of A1 to 90 wt.-% to 5 wt.-% of A2 based on the weight of A1 and A2. In one aspect of the invention, the ration of A1 to A2 is in the range of from 45 wt.-% to 90 wt.-% A1 to 55 wt.-% to 10 wt.-% of A2 based on the weight of A1 and A2.

In an aspect of the present invention the copolymer A1 is a rubber free styrene-acrylonitrile copolymer.

In another aspect of the present invention, the styrene-acrylonitrile copolymer A1 is prepared from at least one first monomer selected from the group consisting of styrene, alpha-methylstyrene, and mixtures thereof, and from a second monomer which is acrylonitrile. In a further aspect the styrene-acrylonitrile copolymer A1 comprises at least 10 wt.-% based on the total weight of component A1 of styrene. In another aspect copolymer A1 comprises at least 50 wt.-% based on the total weight of component A1 of styrene. In a further aspect copolymer A1 comprises at least 60 wt.-% based on the total weight of component A1 of styrene. In even another aspect copolymer A1 comprises at least 65 wt.-% based on the total weight of component A1 of styrene.

In one aspect of the present invention, the styrene-acrylonitrile copolymer component A1 has an acrylonitrile content of from 5 to 35 wt.-% based on the total weight of the styrene-acrylonitrile copolymer component A1. In another aspect, the styrene-acrylonitrile copolymer component A1 has an acrylonitrile content of from 15 to 35 wt.-% based on the total weight of the styrene-acrylonitrile copolymer component A1. In a further aspect the styrene-acrylonitrile copolymer component A1 has an acrylonitrile content of from 22 to 35 wt.-% based on the total weight of the styrene-acrylonitrile copolymer component A1.

In a further aspect of the present invention the styrene-acrylonitrile copolymer A1 is prepared from 50 to 96 wt.-% based on the total weight of copolymer A1 of styrene and/or alpha-methylstyrene and 4 to 50 wt.-% based on the total weight of copolymer A1 of acrylonitrile. In another aspect the styrene-acrylonitrile copolymer A1 is prepared from 60 to 85 wt.-% based on the total weight of copolymer A1 of styrene and/or alpha-methylstyrene and 15 to 40 wt.-% based on the total weight of copolymer A1 of acrylonitrile. In another aspect the styrene-acrylonitrile copolymer A1 is prepared from 65 wt. % based on the total weight of copolymer A1 of styrene and 35 wt.-% based on the total weight of copolymer A1 of acrylonitrile.

In one aspect of the present invention the weight average molecular weight M_(w) of the styrene-acrylonitrile copolymer A1 ranges of from 20,000 to 200,000 g/mol. In another aspect the intrinsic viscosity [η] of the styrene-acrylonitrile copolymer A1 is of from 20 to 110 ml/g, determined in dimethylformamide (DMF) at 25° C. In another aspect the viscosity number VN of the styrene-acrylonitrile copolymer A1 is of from 50 to 100 cm³/g determined according to DIN 53726. In even another aspect, the viscosity number is in the range of from 55 to 85 cm³/g.

The synthesis of styrene-acrylonitrile copolymers A1 is for example described in DE-A 24 20 358 and DE-A 27 24 360. Styrene-acrylonitrile copolymers are also described in DE-A 1 971 3509.

The copolymer A1 can be prepared according to the methods known in the art such as by radical polymerization, for example by emulsion polymerization, suspension polymerization, polymerization in solution or polymerization in mass.

The acrylonitrile styrene acrylate graft copolymer A2 comprises spherical particles of crosslinked acrylate rubber A2.1 that are chemically grafted with styrene acrylonitrile copolymer chains A2.2.

In one aspect of the invention, the acrylonitrile styrene acrylate graft copolymer A2 comprises of from 50 to 90 wt.-% based in the total weight of A2 of spherical particles of crosslinked acrylate rubber graft base A2.1 and of from 10 to 50 wt.-% based on the total weight of A2 of graft of styrene acrylonitrile copolymer chains A2.2

The acrylate rubber graft base A2.1 may comprise

-   -   (i) of from 70 to 99.9 wt.-% based on the total weight of A2.1         of at least one C₁ to C₈-alkyl(meth)acrylate,     -   (ii) of from 0 to 29.5 wt.-% based on the total weight of A2.1         of at least one further monomer selected from the group         consisting of styrene, alpha-methylstyrene, C₁- to         C₄-alkylstyrene, acrylonitrile, methacrylonitrile, isoprene,         butadiene, chloroprene, methylmethacrylate,         alkylenglycoledi(meth)acrylate, and vinylmethylether; and     -   (iii) of from 0.1 to 10 wt.-% based on the total weight of A2.1         of at least one di- or polyfunctional crosslinking agent.

The graft of styrene acrylonitrile copolymer chains A2.2 may comprise

-   -   (iv) of from 50 to 100 wt.-% based on the total weight of the         graft A2.2 of at least one monomer selected from the group         consisting of styrene, alpha-methylstyrene, p-methylstyrene, C₁         to C₄-alkyl(meth)acrylate, and     -   (v) of from 0 to 50 wt.-% based on the total weight of the graft         A2.2 of at least one monomer selected from the group consisting         of acrylonitrile, methacrylnitril, acrylamide, vinylmethyl         ether, anhydrides of unsaturated carboxylic acids such as maleic         acid anhydride, phthalic acid anhydride, and imides of         unsaturated carboxylic acids such as N-cyclohexylmaleimide and         N-phenylmaleimide.

In one aspect of the present invention, component A2 comprise a graft base A2.1 of from 40 to 90 wt.-% based on the total weight of the impact-modified graft rubber acrylonitrile styrene acrylate A2 comprising

-   (i) from 70 to 99.9 wt.-% of n-butyl acrylate based on the total     weight of A2.1, -   (ii) from 0 to 30 wt.-% of styrene based on the total weight of     A2.1, -   (iii) from 0.1 to 5 wt.-% of a crosslinking agent based on the total     weight of A2.1; and a graft A2.2 of from 10 to 60 wt.-% comprising -   (iv) from 65 to 95 wt.-% based on the total weight of A2.2 of     styrene, and -   (v) from 5 to 35 wt.-% based on the total weight of A2.2 of     acrylonitrile.

The term crosslinking agent is to be understood to describe a compound with at least two double bonds, for example chemically different double bonds, such as one acrylic double bond. In one aspect of the present invention the crosslinking agent is selected from the group consisting of allyl(meth)acrylate, divinylbenzene, diallylmaleate, diallylfumarate, diallylpthalate, triallylcyanurat, triallylisocyanurat, and dicyclopentadienyl acrylate. In another aspect of the present invention the crosslinking agent is allyl methacrylate (AMA) and/or dicyclopentadienyl acrylate (DCPA).

In another aspect of the present invention the graft base A2.1 comprises of from 90 to 99.9 wt.-%, based on the total weight of the graft base A2.1, of n-butyl acrylate. In a further aspect, the graft base A2.1 comprises of from 1 to 10 wt.-%, based on the total weight of the graft base A2.1, of styrene. In another aspect the graft base A2.1 comprises of from 0.1 to 2.5 wt.-% of a crosslinking agent based on the total weight of A2.1. In a further aspect the graft base A2.1 comprises of from 0.4 to 2.1 wt.-% of a crosslinking agent based on the total weight of A2.1.

In another aspect of the present invention, the average particle size d₅₀ of the acrylonitrile styrene acrylate graft copolymer A2, determined using an ultracentrifuge, is generally of from 50 to 1000 nm. In a further aspect the average particle size d₅₀ of the acrylonitrile styrene acrylate graft copolymer A2 is of from 60 to 850 nm. In another aspect the average particle size d₅₀ of the acrylonitrile styrene acrylate graft copolymer A2 is of from 90 to 700 nm. In even another aspect the average particle size d₅₀ of the acrylonitrile styrene acrylate graft copolymer A2 is particularly of from 70 to 700 nm. In a further aspect of the present invention, the acrylonitrile styrene acrylate graft copolymer A2 comprises different particles with different mean particle diameters, one acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 50 to 180 nm, and a second acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 200 to 800 nm.

In another aspect the acrylonitrile styrene acrylate graft copolymer A2 comprises one acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 80 to 150 nm, and a second acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 300 to 700 nm. In one aspect of the present invention, the different acrylonitrile styrene acrylate graft copolymers A2 are prepared by individually grafting different graft bases A2.1 with the different grafts A2.2. In even another aspect the acrylonitrile styrene acrylate graft copolymer A2 comprises one acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 90 to 100 nm, and a second acrylonitrile styrene acrylate graft copolymer A2 having a mean particle diameter d₅₀ of from 400 to 600 nm. In a further aspect one acrylonitrile styrene acrylate graft copolymer A2 is desired to have a narrow particle size distribution Q calculated from (d₉₀-d₁₀)/d₅₀ being less than 0.3. In another aspect Q is less than 0.2.

The particle size of latex particles can be controlled during synthesis by suitable means as disclosed for example in DE-A 28 26 925.

Typically mean particle size can be measured by ultracentrifugation as described in W. Scholtan et al., Kolloid-Z. u. Z. Polymere 250, pages 782 to 796, 1972 or using Hydrodynamic Chromatigraphy (HDC) as disclosed in W. Wohlleben et al., “Measurement of Particle Size Distribution of Polymer Latexes”, 2010, Editors: L. Gugliotta, J. Vegam p. 130-153. The mean particle diameter d₅₀ represents the diameter value of the particle size distribution curve where 50 vol.-% have a larger diameter compared to the d₅₀ value. In similar way for example the d₉₀ value gives the particle diameter where 90 vol.-% of all particles have a smaller diameter.

The mean particle size (mass mean; d_(w)) can also be determined by turbidity measurement as described in Lange, Kolloid-Z. u. Z. Polymere, Band 223, Heft 1.

In a further aspect of the present invention, the thermoplastic resin composition comprises of from 1 to 70 wt.-% based on the total weight of components A1 and A2 of at least one thermoplastic polymer A3 selected from polycarbonate (PC), polyamide (PA), and mixtures thereof. In another aspect, the thermoplastic resin composition comprises of from 0 to 50 wt.-% based on the total weight of the ASA components A1 and A2 of at least one thermoplastic polymer A3 selected from polycarbonate (PC), polyamide (PA) and mixtures thereof.

In a further aspect of the invention, the thermoplastic resin composition comprises of from 10 to 50 wt.-% based on the total weight of components A1 and A2 of at least one thermoplastic polymer A3 selected from polycarbonate (PC), polyamide (PA), and mixtures thereof. In even another aspect of the invention, the thermoplastic resin composition comprises of from 20 to 40 wt.-% based on the total weight of components A1 and A2 of at least one thermoplastic polymer A3 selected from polycarbonate (PC), polyamide (PA), and mixtures thereof.

In another aspect of the present invention, the thermoplastic polymer A3 is selected from the group consisting of polycarbonate (PC), polyamide (PA), and mixtures thereof.

Polycarbonate includes one or more, in another aspect one or two, in a further aspect one aromatic polycarbonate. Aromatic polycarbonate includes for example polycondensation products, for example aromatic polycarbonates, aromatic polyester carbonates. According to the invention suitable aromatic polycarbonates and/or aromatic polyester carbonates are known from the literature or may be prepared by processes known from the literature (for the preparation of aromatic polycarbonates see, for example, Schnell, “Chemistry and Physics of Polycarbonates”, Interscience Publishers, 1964 and DE-AS 1 495 626, DE-A 2 232 877, DE-A 2 703 376, DE-A 2 714 544, DE-A 3 000 610 and DE-A 3 832 396; for the preparation of aromatic polyester carbonates e.g. DE-A 3 077 934).

The preparation of aromatic polycarbonates is carried out e.g. by reaction of diphenols with carbonic acid halides, in another aspect phosgene, and/or with aromatic dicarboxylic acid dihalides, in another aspect benzenedicarboxylic acid dihalides, by the phase interface process, optionally using chain terminators, for example monophenols, and optionally using branching agents.

These are trifunctional or more than trifunctional, for example triphenols or tetraphenols. A preparation via a melt polymerization process by reaction of diphenols with, for example, diphenyl carbonate is also possible.

In one aspect diphenols are hydroquinone, resorcinol, dihydroxydiphenols, bis(hydroxyphenyl)-C₁-C₅-alkanes, bis-(hydroxyphenyl)-C₅-C₆-cycloalkanes, bis(hydroxyphenyl)ethers, bis-(hydroxyphenyl)sulfoxides, bis-(hydroxyphenyl)ketones, bis(hydroxyphenyl)sulfones and α,α-bis-(hydroxyphenyl)-diisopropyl-benzenes and nucleus-brominated and/or nucleus-chlorinated derivatives thereof. In a further aspect diphenols are 4,4′-dihydroxydiphenyl, bisphenol A, 2,4-bis-(4-hydroxyphenyl)-2-methylbutane, 1,1-bis-(4-hydroxyphenyl)-cyclohexane, 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl sulfone and di- and tetrabrominated or chlorinated derivatives thereof, such as, for example, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)propane or 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane. In another aspect 2,2-bis(4-hydroxyphenyl)-propane (bisphenol A) is used. The diphenols may be employed individually or as any desired mixtures. The diphenols are known from the literature or obtainable by processes known from the literature.

Chain terminators which are suitable for the preparation of the thermoplastic, aromatic polycarbonates are, for example, phenol, p-chlorophenol, p-tert-butylphenol or 2,4,6-tribromophenol, and also long-chain alkylphenols, such as 4-[2-(2,4,4-trimethylpentyl)]-phenol, 4-(1,3-tetramethylbutyl)-phenol according to DE-A 2 842 005 or monoalkylphenols or dialkylphenols having a total of 8 to 20 carbon atoms in the alkyl substituents, such as 3,5-di-tert-butylphenol, p-iso-octylphenol, p-tert-octylphenol, p-dodecylphenol and 2-(3,5-dimethylheptyl)-phenol and 4-(3,5-dimethylheptyl)-phenol. The amount of chain terminators to be employed is in general between of from 0.5 mol-% and 10 mol %, based on the sum of the moles of the particular diphenols employed.

The thermoplastic, aromatic polycarbonates have weight-average molecular weights (M_(W), measured e.g. by ultracentrifuge or scattered light measurement) of from 10.000 to 200.000 g/mol, in another aspect 15.000 to 80.000 g/mol, in a further aspect 24.000 to 32.000 g/mol. The thermoplastic, aromatic polycarbonates may be branched in a known manner, and in another aspect by incorporation of from 0.05 to 2.0 mol-%, based on the sum of the diphenols employed, of compounds which are trifunctional or more than trifunctional, for example those having three and more phenolic groups. Both homopolycarbonates and copolycarbonates are suitable.

It is also possible of from 1 to 25 wt.-%, in another aspect 2.5 to 25 wt.-%, based on the total amount of diphenols to be employed, of polydiorganosiloxanes having hydroxy-aryloxy end groups to be employed for the preparation of copolycarbonates according to the invention according to component A. These are known (U.S. Pat. No. 3,419,634) and may be prepared by processes known from the literature. The preparation of copolycarbonates containing polydi-organosiloxanes is described in DE-A 3 334 782. In another aspect polycarbonates are, in addition to the bisphenol A homopolycarbonates, the copolycarbonates of bisphenol A with up to 15 mol-%, based on the sum of the moles of diphenols, of other diphenols mentioned, in a further aspect 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Aromatic dicarboxylic acid dihalides for the preparation of aromatic polyester carbonates are in another aspect the diacid dichlorides of isophthalic acid, terephthalic acid, di-phenyl ether-4,4′-dicarboxylic acid and of naphthalene-2,6-dicarboxylic acid. Mixtures of the diacid dichlorides of isophthalic acid and of terephthalic acid are in a ratio of from between 1:20 and 20:1. A carbonic acid halide, in another aspect phosgene, is additionally co-used as a bifunctional acid derivative in the preparation of polyester carbonates. Possible chain terminators for the preparation of the aromatic polyester carbonates are, in addition to the monophenols already mentioned, also chlorocarbonic acid esters thereof as well as the acid chlorides of aromatic monocarboxylic acids, which may optionally be substituted by C₁ to C₂₂-alkyl groups or by halogen atoms, as well as aliphatic C₂ to C₂₂-monocarboxylic acid chlorides. The amount of chain terminators is in each case of from 0.1 to 10 mol-%, based on the moles of diphenol in the case of the phenolic chain terminators and on the moles of dicarboxylic acid dichloride in the case of monocarboxylic acid chloride chain terminators. The aromatic polyester carbonates may also contain incorporated aromatic hydroxycarboxylic acids.

The aromatic polyester carbonates may be either linear or branched in a known manner (in this context see DE-A 2 940 024 and DE-A 3 007 934). Branching agents which may be used are, for example, carboxylic acid chlorides which are trifunctional or more than trifunctional, such as trimesic acid trichloride, cyanuric acid trichloride, 3,3′,4,4′-benzophenone-tetracarboxylic acid tetrachloride, 1,4,5,8-naphthalenetetracarboxylic acid tetrachloride or pyromellitic acid tetrachloride, in amounts of from 0.01 to 1.0 mol % (based on the dicarboxylic acid dichlorides employed), or phenols which are trifunctional or more than trifunctional, such as phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-hept-2-ene, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-tri(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)phenylmethane, 2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propane, 2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol, tetra-(4-hydroxyphenyl)-methane, 2,6-bis-(2-hydroxy-5-methyl-benzyl)-4-methyl-phenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane, tetra-(4-[4-hydroxyphenyl-isopropyl]-phenoxy)-methane and 1,4-bis-[4,4′-dihydroxy-triphenyl)methyl-]benzene, in amounts of from 0.01 to 1.0 mol-%, based on the diphenols employed. Phenolic branching agents may be initially introduced into the reaction vessel with the diphenols, and acid chloride branching agents may be introduced together with the acid dichlorides.

The content of carbonate structural units in the thermoplastic, aromatic polyester carbonates may be varied as desired. In one aspect, the content of carbonate groups is up to 100 mol-%, in another aspect up to 80 mol-%, in a further aspect up to 50 mol-%, based on the sum of ester groups and carbonate groups. Both the ester and the carbonate content of the aromatic polyester carbonates may be present in the polycondensate in the form of blocks or in random distribution.

The relative solution viscosity (η_(rel)) of the aromatic polycarbonates and polyester carbonates is in the range of from 1.18 to 1.4, in another aspect 1.20 to 1.32 (measured on solutions of 0.5 g polycarbonate or polyester carbonate in 100 ml methylene chloride solution at 25° C.). The thermoplastic, aromatic polycarbonates and polyester carbonates may be employed by themselves, or in any desired mixture of one or more, or in another aspect one to three, or one or two thereof. In a further aspect only one type of polycarbonate is used.

In even another aspect the aromatic polycarbonate is a polycarbonate based on bisphenol A and phosgene, which includes polycarbonates that have been prepared from corresponding precursors or synthetic building blocks of bisphenol A and phosgene. These aromatic polycarbonates may be linear or branched due to the presence of branching sites.

Suitable polyamides are known homopolyamides, copolyamides and mixtures of such polyamides. They may be semi-crystalline and/or amorphous polyamides. Suitable semi-crystalline polyamides are polyamide-6, polyamide-6,6, mixtures and corresponding copolymers of those components. Also included are semi-crystalline polyamides the acid component of which consists wholly or partially of terephthalic acid and/or isophthalic acid and/or suberic acid and/or sebacic acid and/or azelaic acid and/or adipic acid and/or cyclohexanedicarboxylic acid, the diamine component of which consists wholly or partially of m- and/or p-xylylene-diamine and/or hexamethylenediamine and/or 2,2,4-trimethylhexamethylenediamine and/or 2,2,4-trimethylhexamethylenediamine and/or isophoronediamine, and the composition of which is in principle known.

Mention may also be made of polyamides that are prepared wholly or partially from lactams having from 7 to 12 carbon atoms in the ring, optionally with the concomitant use of one or more of the above-mentioned starting components.

In another aspect semi-crystalline polyamides are polyamide-6 and polyamide-6,6 and mixtures thereof. Known products may be used as amorphous polyamides. They are obtained by polycondensation of diamines, such as ethylenediamine, hexamethylenediamine, decamethylenediamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, m- and/or p-xylylene diamine, bis-(4-aminocyclohexyl)-methane, bis-(4-aminocyclohexyl)-propane, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 2,5- and/or 2,6-bis-(aminomethyl)-norbornane and/or 1,4-diaminomethylcyclohexane, with dicarboxylic acids such as oxalic acid, adipic acid, azelaic acid, azelaic acid, decanedi-carboxylic acid, heptadecanedicarboxylic acid, 2,2,4- and/or 2,4,4-trimethyladipic acid, isophthalic acid and terephthalic acid. Also suitable are copolymers obtained by poly-condensation of a plurality of monomers, as well as copolymers prepared with the addi-tion of aminocarboxylic acids such as ε-aminocaproic acid, ω-aminoundecanoic acid or ω-aminolauric acid or their lactams.

In a further aspect suitable amorphous polyamides are the polyamides prepared from isophthalic acid, hexamethylenediamine and further di-amines such as 4,4′-diamino-dicyclohexylmethane, isophoronediamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, 2,5- and/or 2,6-bis-(aminomethyl)-norbornene; or from isophthalic acid, 4,4′-diamino-dicyclohexylmethane and ε-caprolactam; or from isophthalic acid, 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane and laurinlactam; or from terephthalic acid and the isomeric mixture of 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine. Instead of pure 4,4′-diaminodicyclohexylmethane it is also possible to use mixtures of the position-isomeric diaminodicyclohexylmethanes, which are composed of from 70 to 99 mol-% of the 4,4′-diamino isomer, of from 1 to 30 mol-% of the 2,4′-diamino isomer, of from 0 to 2 mol-% of the 2,2′-diamino isomer and optionally corresponding to more highly condensed diamines, which are obtained by hydrogenation of industrial grade diaminodiphenylmethane. Up to 30% of the isophthalic acid may be replaced by terephthalic acid.

In one aspect, the polyamides have a relative viscosity (measured on a 1 wt.-% solution in m-cresol or 1% (weight/volume) solution in 96 wt.-% sulfuric acid at 25° C.) of from 2.0 to 5.0, in a further aspect of from 2.5 to 4.0.

The pigment component B is used for coloring the thermoplastic resin composition either by at least one colorant or at least one pigment.

Examples for suitable colorants include all dyes that may be used for transparent, semi-transparent, or non-transparent coloring of styrene copolymers. Any pigment suitable for this purpose can be used. Pigments are either organic or inorganic pigments. Examples for suitable pigments include titanium dioxide, phthalocyanines, ultramarine blue, iron oxides, carbon black, and the entire class of organic pigments. In one aspect of the present invention pigment B is an inorganic pigment. In another aspect of the present invention, pigment B is a metal-based pigment. In a further aspect of the present invention, pigment B is a transition metal based pigment. In a preferred aspect of the present invention, iron based pigments such as iron oxide based pigments are used.

The at least one UV light stabilizer C is selected from hindered amine UV light stabilizers (HALS). In one aspect of the present invention, the thermoplastic resin composition according to any of the previous claims, wherein component C is a hindered amine UV light stabilizer according to the following formula (Ia) and/or formula (Ib):

wherein R1 is H or methyl; each R2 is individually selected from the group consisting of hydrogen, methyl, and ethyl; R3 is selected from the group consisting of linear C₁- to C₁₈-esters which are connected to formula (Ia) via the oxygen atom of the ester function; and with R4 being selected from the group consisting of C1 to C10 alkylene.

In another aspect of the present invention, the HALS component C is selected from the group consisting of a compound according to formula (II), a compound according to formula (III), and mixtures thereof.

This sterically hindered amine according to formula (II) (CAS Number 52829-07-9) and its preparation are known to the skilled person and described in the literature (see, for example, U.S. Pat. No. 4,396,769 and the literature references cited therein). It is sold by BASF SE under the Tinuvin® 770 name.

The sterically hindered amine according to formula (III) (CAS Number 167078-06-0) and its preparation from 2,2,6,6-tetra-methyl-4-piperinol and stearic and/or palmitic acid are known to the skilled person and described in the literature (Carlsson et al., Can. Journal of Polymer Science, Polymer Chemistry Edition (1982), 20(2), 575-82). It is sold by Cytec Industries under the Cyasorb® 3853 name.

Another example for hindered amine UV light stabilizers are compounds formula (IV):

This sterically hindered amine (CAS Number 71878-19-8) and its preparation are known to the skilled worker and described in the literature (see, for example, EP-A 093 693 and the literature references cited therein). It is sold by BASF SE under the Chimassorb® 944 name.

A further example for a hindered amine UV light stabilizer is the compound of the formula (V):

In this formula, n is of from 2 to 25. In another aspect of the invention n is of from 2 to 20. In a further aspect n is of from 2 to 15.

This sterically hindered amine (CAS Number 101357-37-3) and its preparation are known to the skilled worker and described in the literature (see U.S. Pat. No. 5,208,132 and the literature references cited therein). It is sold by ADEKA under the Adeka Stab® LA-68 name.

A further example for a hindered amine UV light stabilizer is the compound of the formula (VI):

In this formula, n is of from 2 to 25. In another aspect of the invention n is of from 2 to 20. In a further aspect n is of from 2 to 15.

This sterically hindered amine (CAS Number 82451-48-7) and its preparation are known to the skilled worker and described in the literature (see, for example, U.S. Pat. No. 4,331,586 and the literature references cited therein). It is sold by Cytec Industries under the Cyasorb® UV-3346 name.

A further example for a hindered amine UV light stabilizer is the compound of the formula (VII):

In this formula, n is of from 2 to 25. In another aspect of the invention n is of from 2 to 20. In a further aspect n is of from 2 to 15.

This sterically hindered amine (CAS Number 192268-64-7) and its preparation are known to the skilled worker and described in the literature (see, for example, EP-A 782 994 and the literature references cited therein). It is sold by BASF under the Chimassorb® 2020 name.

In all aspects of the present invention, only hindered amine UV light stabilizers C are present in the thermoplastic resin composition. This is to be understood that less than 10 wt.-% of UV stabilizers or absorbers based on the total weight of UV stabilizers C other than UV stabilizers of the HALS class are present in the thermoplastic resin composition of the present invention. In another aspect of the present invention, only 2 wt. % of UV stabilizers or absorbers based on the total weight of UV stabilizers C other than UV stabilizers of the HALS class are present in the thermoplastic resin composition of the present invention. In a further aspect less than 0.1 wt.-% of UV stabilizers or absorbers based on the total weight of UV stabilizers C other than UV stabilizers of the HALS class are present in the thermoplastic resin composition of the present invention.

If present, the at least one polymer additive D is selected from the group consisting of oxidation retarders, agents to counter thermal decomposition, lubricants and mold release agents, fibrous and pulverulent fillers, reinforcing agents, nucleating agents, metal scavengers and plasticizers. Polymer additives D are different from any component B and C.

Examples of oxidation retarders and heat stabilizers are halides of the metals from group I of the periodic table, examples being sodium, potassium and/or lithium halides, optionally in combination with copper(I) halides, e.g., chlorides, bromides, iodides, sterically hindered phenols, hydroquinones, different substituted representatives of these groups, and mixtures thereof, in concentrations of up to 1 wt.-%, based on the weight of the polymer blend according to the present invention.

Furthermore fibrous and pulverulent fillers and reinforcing agents are used. Examples of the latter are carbon fibers, glass fibers, amorphous silica, calcium silicate (wollastonite), aluminum silicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, and feldspar.

Examples of nucleating agents that can be used are talc, calcium chloride, sodium phenylphosphinate, aluminum oxide, and silicon dioxide.

Examples of lubricants and mold release agents, which can be used in general in amounts up to 1 wt.-%, are long-chain fatty acids such as stearic acid or behenic acid, their salts (e.g., Ca or Zn stearate) or esters (e.g., stearyl stearate or pentaerythrityl tetrastearate), and also amide derivatives (e.g., ethylenebisstearylamide). For better processing, mineral-based antiblocking agents may be added in amounts up to 0.1 wt. % to the molding compositions of the invention. Examples include amorphous or crystalline silica, calcium carbonate, or aluminum silicate.

Processing aids which can be used are, for example, mineral oil such as white oil.

Examples of plasticizers include dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils, N-(n-butyl)benzenesulfonamide, and o- and p-tolylethylsulfonamide.

For further improving the resistance to inflammation, it is possible to add all of the flame retardants known for the thermoplastics in question, more particularly those flame retardants based on phosphorus compounds and/or on red phosphorus itself.

In one aspect of the present invention the thermoplastic resin composition comprises at least one component D which is a metal scavenger. Metal scavengers are characterized in that they comprise reactive ligands which are capable of complexing metal ions. The reactive ligands may be attached to a small molecule or to a polymeric, often inert backbone. In one embodiment of the present invention, the metal scavenger component D comprises at least one hydrazide group. In a further aspect of the present invention, the metal scavenger component D is a component according to formula (VIII):

wherein R15 and R16 are independently from each other selected from a linear or branched C₂- to C₁₀-alkanediylgroup, R5 to R14 are independently from each other selected from the group consisting of hydrogen, a linear or branched C₁- to C₁₀-alkyl group, an amine group, an either monosubstituted or disubstituted, linear or branched C₁- to C₁₀-monoamine or diamine, a hydroxyl group, an alkoxy group with a linear or branched C₁- to C₁₀-alkyl group, a carboxylic group, an ester group with a linear or branched C₁- to C₁₀-alkyl group, a thiol, a mercaptane with a linear or branched C₁- to C₁₀-alkyl group. In one aspect of the present invention, R5 to R14 are independently from each other selected from the group consisting of hydrogen, a linear or branched C₁- to C₁₀-alkyl group, and a hydroxyl group. In a further aspect of the present invention, R5 to R14 are independently from each other selected from the group consisting of linear or branched C₂- to C₈-alkyl group. In even another aspect of the present invention, R5 to R14 are independently from each other selected from the group consisting of linear or branched C₂- to C₅-alkyl group.

In a further aspect R5, R9, R10, and R14 are independently from each other hydrogen or methyl, R6, R8, R11, R13 are independently from each other C₂- to C₈-alkyl, and R7, and R12 are independently from each other hydroxy or C₁- to C₁₀-alkoxy groups. In a further aspect R5, R9, R10, and R14 are hydrogen, R6, R8, R11, R13 are tert.-butyl, and R7, and R12 are hydroxy groups.

In another aspect, the metal scavenger D is the compound according to formula IX:

The thermoplastic resin composition according to the present invention show improved resistance under artificial weathering conditions. This can for example be quantified by applying standardized artificial weathering tests as disclosed in DIN ISO-4892-2 or DIN ISO 4892-3 by comparing the color shift dE of inventive samples and of comparative samples. This is for example done after 6000 h of artificial weathering. In one aspect of the present invention the composition shows a color shift dE of equal to or lower than 3.0 upon UV irradiation according to ISO-4892-2 after 6000 hours. In a further aspect of the present invention the composition shows a color shift dE of equal to or lower than 2.0 upon UV irradiation according to ISO-4892-2 after 6000 hours.

In another aspect of the present invention the composition shows a color shift dE of equal to or lower than 1.5 upon UV irradiation according to ISO-4892-2 after 6000 hours.

In one aspect the composition shows a color shift dE of equal to or lower than 2.5 upon UV irradiation according to ISO-4892-3 after 6000 hours. In another aspect the composition shows a color shift dE of equal to or lower than 2.0 upon UV irradiation according to ISO-4892-3 after 6000 hours. In a further aspect the composition shows a color shift dE of equal to or lower than 1.5 upon UV irradiation according to ISO-4892-3 after 6000 hours.

The color shift dE was calculated as disclosed in DIN ISO-5033-2 with a Datacolor spectral photometer 110.

The present invention further relates to a method for the preparation of the thermoplastic resin composition according to the invention.

The thermoplastic resin composition according to the invention can generally be obtained by any usual method, comprising the step of mixing components A1, A2, B, C, and optionally A3 and D at temperatures of from 100° C. to 300° C. and a pressure of from 1 to 150 bar, e.g. in random order, followed by a kneading or extrusion step.

Mixing apparatuses used are those known to the skilled person. Components A1, A2, B, C, and optionally A3 and D may be mixed, for example, by joint extrusion, kneading, or rolling.

Examples of mixing apparatus for implementing the method includes discontinuously operating, heated internal kneading devices with or without ram-feeder, continuously operating kneaders, such as continuous internal kneaders, screw kneaders with axially oscillating screws, Banbury kneaders, furthermore extruders, and also roll mills, mixing roll mills with heated rollers, and calenders. In one aspect of the invention, the mixing apparatus used is an extruder. Particularly suitable for melt extrusion are, for example, single-screw or twin-screw extruders. In a further aspect of the invention a twin-screw extruder is used.

In some cases the mechanical energy introduced by the mixing apparatus in the course of mixing is enough to cause the mixture to melt, meaning that the mixing apparatus does not have to be heated. Otherwise, the mixing apparatus is generally heated.

The temperature is guided by the chemical and physical properties of components A1, A2, B, C, and optionally A3 and D, and should be selected such as to result in a substantially liquid-melt polymer mixture. On the other hand, the temperature is not to be unnecessarily high, in order to prevent thermal damage of the polymer mixture.

The mechanical energy introduced may, however, also be high enough that the mixing apparatus may even require cooling. Mixing apparatus is operated customarily at of from 160 to 400° C., in another aspect of from 180 to 300° C.

In one aspect of the invention, mixing can be performed for example by joint extrusion and calendering. The calendering is expediently carried out firstly in kneaders or extruders (softening) and, if desired, on mixing rolls, followed by the actual calendering process with, if desired, addition of suitable stabilizers. Blowmolding and injection molding are carried out on the usual machinery.

In one aspect of the invention, the extrusion of the thermoplastic resin composition according to the present invention is carried out in an extruder at a temperature above 100° C. In another aspect of the present invention the feeding zone of the single- or twin-screw extruder is set to a temperature in the range of from 100 to 180° C., the mixing/kneading zones to of from 180 to 250° C. and the final zones to of from 220 to 270° C. Nozzle temperature is set to a temperature in the range of from 240 to 280° C. In a further aspect, the nozzle temperature is set to a temperature in the range of from 255 to 265° C. Tool temperature is set to a temperature in the range of from 50 to 100° C. In one aspect of the invention, tool temperature is set in the range of from 60 to 80° C. Screw speed is set in the range of from 300 to 500 rpm. Injection pressure is set in the range of from 50 to 120 bar. In another aspect of the invention, injection pressure was set in the range of from 80 to 110 bar.

For workup the extruder can be equipped with a hole-plate, water-bath and pelletizer for making pellets or micro-pellets.

Another aspect of the present invention is related to the method for preparation the thermoplastic resin composition according to the present invention wherein at least two of components A1, A2, B, C, and optionally A3 and D are premixed to form a masterbatch.

Another aspect of the invention relates to the use of the thermoplastic resin composition for the preparation of molded articles, such as articles used for cars or electronic devices.

A further aspect of the invention relates to molded articles prepared from the thermoplastic resin composition according the present invention.

The molded article can be used in various fields of applications such as household items, electronic components, household equipment, garden equipment, medicaltechnology equipment, automotive parts, motor-vehicle components, building and construction, and bodywork parts. In another aspect the polymer blend as described above can be used for the production by injection molding of a automotive part, a household part, wall sidings, or roof tiles.

The following examples and claims further illustrate the invention.

Raw Materials

Luran® S 776 SE is a commercially available ASA copolymer from INEOS Styrolution (Frankfurt).

Palatinol 10-P (phthalic acid ester of 010 alcohols) can be purchased from BASF SE. Colortherm Red 110M is a micronized iron oxid red pigment, commercially available by Supplier Lanxess (Germany), produced according to Laux process.

Tinuvin P (2-(2H-benzotriazol-2-yl)-p-cresol, CAS-No. 2440-22-4) is a commercial UV-absorber that can be purchased from BASF SE. Tinuvin® 770 (Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, CAS-No. 52829-07-9) can be purchased from BASF SE.

Sample Preparation

For compounding a Coperion ZSK 25 extruder was used and for injection molding an Arburg machine. All test specimens have the following dimensions: 75×50 mm.

Testing

Artificial weathering according to ISO 4892-2A(1) was conducted under the following conditions:

Irradiance wavelength nm 300 to 400 340 Light strength W/m² 60 ± 2  0.51 ± 0.02 Black board temperature ° C. 65 ± 3  Relative humidity % 50 ± 10 Cycle time for Duration for min  18 water spray water spray Duration for not min 102 water spray Xenon filter Inner — Boro. S. (S-type) combination outer — Boro. S. (S-type)

For artificial weathering according to ISO 4892-3 a Q-UVse tester equipped with UVA-340 lamps was used. Each cycle consists of 8 h irradiation (0.76 W/m², 60° C. black panel temperature) and 4 h condensation (no irradiation, 50° C. black panel temperature).

For color measurements a commercial testing device Datacolor 110 was used.

EXAMPLES

Commercially available ASA-copolymer Luran S 776SE was compounded with the pigment Colortherm Red 110M, the plasticizer Palatinol 10-P and different amounts of UV stabilizers (HALS and UV absorbers (comparative examples only)).

The formulations without UV absorber showed the best results regarding color shift dE after artificial weathering as carried out described further in below.

Samples have been tested according to two different artificial weathering methods: ISO 4892-2 and ISO 4892-3. Total color shift has been measured every 1000 h.

According to both methods the thermoplastic resin according to the present invention containing only a HALS as UV stabilizer (Tinuvin 770) yielded always the lowest color shift.

Comparative Comparative Example Example Example 1 (B) 1 (C) 2 (K) Component A (thermoplastic 96.15 96.15 96.15 resin) Luran S 776SE Component D (additive) 1.44 1.44 1.44 Palatinol 10-P Component B (Pigment) 1.92 1.92 1.92 Iron Oxide Red01 Colortherm Red 110M Component C (HALS) 0.48 0.48 Tinuvin 770 UV absorber Tinuvin P 0.48 0.48 dE after 4000 h (ISO 0.61 7.13 3.12 4892-2) dE after 5000 h (ISO 0.68 8.27 — 4892-2) dE after 6000 h (ISO 1.07 8.39 3.04 4892-2) dE after 5000 h (ISO 1 2 3.4 4892-3) dE after 6000 h (ISO 1.2 2.5 4.3 4892-3) 

1-16. (canceled)
 17. A thermoplastic resin composition comprising: (a1) at least one styrene-acrylonitrile copolymer component A1, (a2) at least one acrylonitrile styrene acrylate graft copolymer A2 as impact modifier, (a3) optionally at least one thermoplastic polymer A3 other than components A1 and A2, (b) at least one transition metal pigment B, (c) at least one hindered amine UV light stabilizer C, and (d) optionally further polymer additives D, other than components B and C, wherein the UV stabilizing component(s) present in the thermoplastic resin are only hindered amine UV light stabilizer(s) C, and wherein the composition shows a color shift dE of equal to or lower than 3.0 upon UV irradiation according to ISO-4892-2 after 6000 hours.
 18. The thermoplastic resin composition according to claim 17, comprising 70.0 to 99.4 wt. %, based on the total weight of the composition, of components A1, A2, and optionally A3, and comprising 0.5 to 7.0 wt.-%, based on the total weight of the composition, of component B, and comprising 0.1 to 1.5 wt.-% based on the total weight of the composition of component C.
 19. The thermoplastic resin composition according to claim 17, comprising (i) of from 89.0 to 99.3 wt.-%, based on the total weight of the composition, of A1, A2, and optionally A3, (ii) of from 0.5 to 7.0 wt.-%, based on the total weight of the composition, of component B, (iii) of from 0.1 to 1.5 wt.-%, based on the total weight of the composition, of at least one hindered amine UV light stabilizer C, and (iv) of from 0.1 to 2.5 wt.-%, based on the total weight of the composition, of at least one further polymer additive D.
 20. The thermoplastic resin composition according to claim 17, wherein the styrene-acrylonitrile copolymer component A1 has an acrylonitrile content of from 5 to 35 wt.-% based on the total weight of the styrene-acrylonitrile copolymer component A1.
 21. The thermoplastic resin composition according to claim 17, wherein the impact-modified graft rubber acrylonitrile styrene acrylate A2 comprises: a graft base A2.1 of from 40 to 90 wt.-% based on the total weight of the impact-modified graft rubber acrylonitrile styrene acrylate A2 comprising: (i) from 70 to 99.9 wt.-% of n-butyl acrylate based on the total weight of A2.1, (ii) from 0 to 30 wt.-% of styrene based on the total weight of A2.1, and (iii) from 0.1 to 5 wt.-% of a crosslinking agent based on the total weight of A2.1; and a graft A2.2 of from 10 to 60 wt.-% comprising: (iv) from 65 to 95 wt.-% based on the total weight of A2.2 of styrene, and (v) from 5 to 35 wt.-% based on the total weight of A2.2 of acrylonitrile.
 22. The thermoplastic resin composition according to claim 17, comprising from 1 to 70 wt. % based on the total weight of components A1 and A2 of at least one thermoplastic polymer A3 selected from the group consisting of polycarbonate (PC), polyamide (PA), and mixtures thereof.
 23. The thermoplastic resin composition according to claim 17, wherein component C is a hindered amine UV light stabilizer according to the following formula (Ia) and/or formula (Ib):

wherein R1 is H or methyl; each R2 is individually selected from the group consisting of hydrogen, methyl, and ethyl; R3 is selected from the group consisting of linear C1- to C18-esters which are connected to formula (Ia) via the oxygen atom of the ester function; and with R4 being selected from the group consisting of C1 to C10 alkylene.
 24. The thermoplastic resin composition according to claim 23, wherein the component C is selected from the group consisting of a compound according to formula (II), a compound according to formula (III), and mixtures thereof


25. The thermoplastic resin composition according to claim 17, wherein at least one component D is a metal scavenger.
 26. The thermoplastic resin composition according to claim 17, wherein the composition shows a color shift dE of equal to or lower than 2.5 upon UV irradiation according to ISO-4892-3 after 6000 hours.
 27. A method for preparing the thermoplastic resin composition according to claim 17, comprising the step of mixing components A1, A2, B, C, and optionally A3, and D at temperatures of from 100° C. to 300° C. and a pressure of from 1 to 150 bar, in any order, followed by a kneading or extrusion step.
 28. The method for preparing the thermoplastic resin composition according to claim 27, wherein at least two of components A1, A2, B, C, and optionally A3, and D are premixed to form a masterbatch.
 29. A molded article prepared from the thermoplastic resin composition according to claim
 17. 